The dwarf nova MM Sco is undergoing a relatively rare outburst as reported by R. Stubbings. YYMMDD(UT) mag observer 970527.438 138 (R. Stubbings) 970527.590 137 (R. Stubbings) MM Sco has a relatively large outburst amplitude (13.0-18.5B in Downes et al. 1997; faint quiescent counterpart indicated, see also Vogt and Bateson 1982, A&AS, 48, 383). GCVS 3 gave a cycle length of >500 days, while GCVS 4 gives 28: days. Vanmunster and Howell's famous "Outburst Activity Database" lists only two outbursts. More observations are clearly needed. Regards, Taichi Kato